Fibre optic cables can be installed along overhead power lines, typically to provide telecommunication links or the means to control or monitor remote sub stations. Installation can take place on the earthwire (i.e. the conductor at the top of a tower system which does not normally carry current) or the phasewire (i.e. one of the current carrying conductors). Installation on the phasewire is the only option where no earthwire exists e.g. on low voltage wood pole lines. These lines typically have three conductors arranged side-by-side. Other arrangements are used and also the support structures are not limited to wood poles e.g. they may be concrete poles or metal lattice structures.
Most poles have spacing insulators which simply hold up the conductors. A schematic view of a spacing insulator is shown in FIG. 1. In that Figure, a fibre optic cable 10 is guided around a spacing insulator 20 upon a pole 30 using a simple channel arrangement 40. The fibre optic cable 10 sits in the channel arrangement 40 and is guided from one side of the pole 30 to the other. The channel arrangement 40 is preferably formed from metal since this ensures that the fibre optic cable 10 is everywhere maintained at the potential of the conductor 50. This in turn prevents leakage currents from flowing along the fibre optic cable 10.
A second form of pole is known as a section pole and is shown in FIG. 2. In that figure, components common to FIGS. 1 and 2 are labelled with like reference numerals.
In the section pole 60 shown in FIG. 2, conductors 50 are anchored to cross members 65 mounted upon the section pole 60. The section pole 60 is braced to support the tension of the conductors 50 (for example by the use of guy wires not shown). Section poles are used in straight sections to limit the ‘domino effect’ should a conductor break. At a section pole, the current passes from one side of the pole 60 to the other via conductive jumpers 70a, 70b, 70c which are usually short sections of the same conductor 50. In this known arrangement the fibre optic cable 10 is secured to the conductive jumper and thereby passes from one side of the pole 60 to the other. Where the line changes direction a similar arrangement is used to deal with the sideways force exerted by the conductors on the pole. This pole is known as an angle pole. The present invention applies equally to both types of pole but for brevity henceforth only section poles will be described.
If maintenance is carried out to the overhead line, then a section of line up to angle or section pole may be de-energised, whilst the adjacent section remains energised. The conductive jumper is detached from one side of the pole so there is a complete mechanical break (and therefore a complete electrical isolation) between the energised and de-energised conductors. The fibre optic cable is unsecured from the conductive jumper so the conductive jumper can be detached.
For the fibre optic cable, two problems arise:                1. it is unsupported and therefore subject to mechanical damage e.g. if conditions should be windy        2. it is subject to the full phase-to-ground potential.        
The present invention seeks to address these and other problems with the art.